Emergence of a New Severe Fever with Thrombocytopenia Syndrome Virus Threat in Northern China: Revealed by First Human Cases and Genomic Data from Inner Mongolia

Despite its known presence in ticks, no laboratory-confirmed human cases had been reported in Inner Mongolia, northern China. This study reports the first isolation and genomic characterization of SFTSV from two human patients in Inner Mongolia.

The two human-derived strains (ZF53-NM-2022 and ZF96-NM-2022) were phylogenetically classified into the C3 genotype. Concurrently, a genetically distinct SFTSV strain (ELH_tick_2024) was identified in local ticks (Dermacentor nuttalli). Comparative genomic analysis revealed that the tick-derived strains exhibited high nucleotide divergence but remarkably high amino acid conservation relative to human-derived strains, suggesting host-associated silent evolution.